Pozzolanic compositions containing coal ash and remediation agents for use in cementitious materials

ABSTRACT

It has been unexpectedly discovered that the addition of a natural or other pozzolan to non-spec coal ash significantly improves the properties of the non-spec coal ash to the extent it can be certified under ASTM C618 and AASHTO 295, as either a Class F or Class C coal ash. The natural pozzolan may be a volcanic ejecta, such as pumice or perlite. Other pozzolans may also be used for this beneficiation process. Many pozzolans are experimentally tested and may be used to beneficiate non-spec coal ash into certifiable Class F coal ash. Additionally, this disclosure provides a method of converting a Class C coal ash to a more valuable Class F coal ash. This discovery will extend diminishing Class F coal ash supplies and turn non-spec coal ash waste streams into valuable, certified coal ash pozzolan which will protect and enhance concrete, mortars and grouts.

PRIORITY DATA

This patent application is a continuation application of U.S. Pat. No.11,299,424, issued on Apr. 12, 2022, which is a continuation of U.S.Pat. No. 10,689,292, issued on Jun. 23, 2020, which is a continuation ofU.S. Pat. No. 10,017,418, issued on Jul. 10, 2018, which is acontinuation of U.S. Pat. No. 9,611,174, issued on Apr. 4, 2017, whichis a continuation of U.S. Pat. No. 9,561,983, issued on Feb. 7, 2017,which is a non-provisional application of U.S. Provisional Patent App.No. 62/016,965, filed on Jun. 25, 2014, each of which is herebyincorporated by reference herein.

FIELD OF THE DISCLOSURE

The present disclosure generally relates to coal ash remediation and/orbeneficiation, pozzolanic compositions for use in concrete, and methodsrelating to the foregoing.

BACKGROUND OF THE DISCLOSURE

Molten lava, flash frozen upon explosive expulsion from the volcanicvent, instantly became what the Romans called “pozzolana”—pumicepozzolan, the key ingredient in Roman concrete. Roman structures such asaqueducts used volcanic ash as pozzolan in their concrete. Concretesusing natural (pumice) pozzolan have proven to last thousands of years.Pozzolans fortify concrete, providing protection by mitigating variousforms of chemical attack such as alkali-silica reaction (ASR), sulfateinduced expansion, efflorescence, as well as rebar oxidation anddebondment caused by the ingress of chlorides. Pozzolans also densifyconcrete, reducing porosity and permeability, thereby reducing chemicalingress and increasing long-term compressive strength and durability.

Fly ash, also known as flue-ash, is one of the residues generated incoal combustion and comprises the fine particles that rise with the fluegases. In an industrial context, fly ash usually refers to ash producedduring combustion of coal. Fly ash is generally captured byelectrostatic precipitators or other particle filtration equipmentbefore the flue gases reach the chimneys of coal-fired power plants.Depending upon the source and makeup of the coal being burned, thecomponents of fly ash vary considerably, but all fly ash includessubstantial amounts of silica (silicon dioxide, SiO₂, alumina (aluminumoxide, Al₂O₃), iron oxide (Fe₂O₃), calcium oxide (CaO), and variousmetals.

In the past, fly ash was generally released into the atmosphere, butpollution control mandated in recent decades now requires that it becaptured prior to release. Fly ash, particularly Class F fly ash, can beused as a pozzolan to enhance hydraulic cement or hydraulic plaster. Flyash can be used as a replacement for some of the Portland cement contentof concrete. Fly ash has historically been available at much lower costthan natural pozzolans as it is a waste material of coal-fired powerplants with associated disposal costs.

Fly ash pozzolan, which is typically less expensive than a naturalpozzolan, is generally used when chemical attack, such as alkali-silicareaction (ASR), is not expected to be severe. Furthermore, fly ashpozzolan is preferred when concrete with a low water-to-cement ratio isdesirable. In general, fly ash creates less water demand than does anatural pozzolan. However, when chemical attack, such as ASR, isexpected to be severe, a natural pozzolan would be a better choice.

Two classes of fly ash are defined by ASTM C618: Class F fly ash andClass C fly ash. The primary difference between these classes is theamount of calcium, silica, alumina, and iron content in the ash. Thechemical properties of the fly ash are largely influenced by thechemical content of the coal burned.

The burning of harder, older anthracite and bituminous coal typicallyproduces Class F fly ash. This fly ash is pozzolanic in nature, andcontains less than 20% lime (CaO). Possessing pozzolanic properties, theglassy silica and alumina of Class F fly ash requires a cementing agent,such as Portland cement, quicklime, or hydrated lime, with the presenceof water in order to react and produce cementitious compounds. Calciumhydroxide (Ca(OH)₂), the major byproduct of the hydraulic reactionbetween cement and water, is the key chemical with which pozzolan reactsto form additional Calcium silicate hydrate (C—S—H), the binder in allPortland cement-based concretes.

Fly ash produced from the burning of younger lignite or subbituminouscoal, Class C fly ash, in addition to having pozzolanic properties, alsohas some self-cementing properties. In the presence of water, Class Cfly ash will harden and gain strength over time. Class C fly ashgenerally contains more than 20% lime (CaO). Unlike Class F fly ash,self-cementing Class C fly ash does not require an activator.

For the coal power industry, concrete has been a convenient market forfly ash. For concrete companies, fly ash has been a low-cost source ofpozzolans. However, recently, a supply problem has started to emerge.Namely, due to increasing environmental regulations of power plants, thequantity and quality of fly ash has been decreasing. There is adeclining availability of fly ash, particularly Class F fly ash, ofsuitable quality for use as a pozzolan in concrete. This situation isexpected to worsen in the coming years.

In view of the challenges in two industries (electrical power andconcrete), what is needed is a method to upgrade the pozzolanic qualityof fly ash. In particular, it would be desirable to generate aremediating or beneficiating agent and process whereby non-certifiable,poor-quality fly ash, often referred to as non-spec fly ash, may beupgraded in quality in order to achieve certification under ASTM C618-12and AASHTO M295.

SUMMARY OF THE DISCLOSURE

In some variations, the present disclosure provides a pozzolaniccomposition for use in concrete, the composition comprising fly ashcombined with a natural pozzolan.

In some embodiments, the natural pozzolan is present in a concentrationof about 1 wt % to about 99 wt %, such as about 10 wt % to about 90 wt%, about 30 wt % to about 70 wt %, about 40 wt % to about 60 wt %, orabout 60 wt % to about 70 wt %.

In some embodiments, a weight ratio of the natural pozzolan to the flyash is from about 0.01 to about 100, such as about 0.1 to about 10, orabout 1 to about 2.

The natural pozzolan may be a pozzolanic, volcanic ash, such as (but notlimited to) a pozzolan derived from tephra, tuff, pumicite or pumice(collectively referred to as “pumice” hereafter) or perlite. In someembodiments, the natural pozzolan is selected from the group consistingof pumice, perlite, metakaolin, diatomaceous earth, ignimbrites,calcined shale, calcined clay, and combinations thereof. Otherby-product pozzolans such as silica fume, ground glass, vitrifiedcalcium alumino-silicates, and high silica content Class F fly ash mayalso be used as remediation or beneficiation agents. Ground granulatedblast furnace slag may, in certain circumstances, also be used as aremediation or beneficiation agent to enhance or improve poor qualitynon-spec fly ash into a fly ash that meets ASTM C618.

In some embodiments, the pozzolanic composition is certified under ASTMC618-12 as a Class F pozzolan. In these or other embodiments, thecomposition may be certified under AASHTO M295 as a Class F pozzolan.

The pozzolanic composition may further comprise an additive to adjustviscosity of the composition. The pozzolanic composition may furthercomprise an additive to adjust water demand of the composition inconcrete.

This disclosure also provides a cementitious mixture comprising apozzolanic composition for use in concrete, the composition comprisingfly ash combined with a natural pozzolan or other pozzolans. In somevariations, a concrete product or structure is provided, comprising anaggregate and the cementitious mixture as disclosed, or a reactionproduct thereof. In some variations, a concrete product or structure isprovided, comprising an aggregate and a pozzolanic composition or areaction product thereof, wherein the pozzolanic composition comprisesfly ash combined with a natural pozzolan or another efficaciouspozzolan.

This disclosure also provides a method of producing a pozzolaniccomposition for use in concrete, the method comprising:

providing a source of fly ash;

providing a natural pozzolan or other efficacious pozzolan; and

combining the fly ash with the natural pozzolan (or other pozzolan), toproduce a pozzolanic composition.

This disclosure also provides a method of upgrading a fly ash as apozzolanic material, the method comprising:

providing a starting fly ash;

providing a natural pozzolan or other efficacious pozzolan; and

combining the starting fly ash with the natural pozzolan (or otherpozzolan), to produce an upgraded fly ash with enhanced pozzolanicproperties compared to the starting fly ash.

This disclosure also provides a method of beneficiating a non-spec flyash or converting a Class C fly ash to a certifiable Class F fly ash,the method comprising:

providing a certified Class C ash or a non-certifiable fly ash;

providing a natural pozzolan or other efficacious pozzolan; and

combining the Class C fly ash or non-certifiable fly ash with thenatural pozzolan (or other pozzolan), to produce a Class F fly ash.

In some method embodiments, the natural or other pozzolan is present ina concentration of about 1 wt % to about 99 wt % in the pozzolaniccomposition, upgraded fly ash, or Class F fly ash. In certainembodiments, the natural or other pozzolan is present in a concentrationof about 10 wt % to about 90 wt %, such as about 30 wt % to about 70 wt%, about 40 wt % to about 60 wt %, or about 60 wt % to about 70 wt % inthe pozzolanic composition, upgraded, enhanced, or converted fly ash, orClass F fly ash.

In these methods, the natural pozzolan may be selected from the groupconsisting of calcined or uncalcined pozzolanic materials such aspumice- or perlite-derived pozzolan, calcined shale, calcined clay,metakaolin, and combinations thereof. Other pozzolans such as silicafume, ground glass, and certified Class F fly ash containing a highpercentage of silica, alumina, and iron may also be used.

In some methods, the pozzolanic composition, upgraded fly ash, or ClassF fly ash is certified under ASTM C618-12. In these or other methods,the pozzolanic composition, upgraded fly ash, or Class F fly ash iscertified under AASHTO M295.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a table of experimental data summarizing compressive strengthsof cementitious materials containing pozzolanic compositions thatinclude various sources of fly ash along with pumice.

FIG. 2 is a table of experimental data summarizing compressive strengthsof cementitious materials containing pozzolanic compositions thatinclude various sources of fly ash along with metakaolin.

FIG. 3 is a table of experimental data summarizing compressive strengthsof cementitious materials containing pozzolanic compositions thatinclude various sources of fly ash along with diatomaceous earth.

FIG. 4 is a table of experimental data summarizing compressive strengthsof cementitious materials containing pozzolanic compositions thatinclude various sources of fly ash along with silica fume.

FIG. 5 is a table of experimental data summarizing compressive strengthsof cementitious materials containing pozzolanic compositions thatinclude various sources of fly ash along with ignimbrite.

FIG. 6 is a table of experimental data summarizing compressive strengthsof cementitious materials containing pozzolanic compositions thatinclude various sources of fly ash along with ground granulatedblast-furnace slag.

FIG. 7 is a table of experimental data summarizing compressive strengthsof cementitious materials containing pozzolanic compositions thatinclude various sources of fly ash along with ultrafine (3 micron)pumice (Source No. 1).

FIG. 8A is a table of experimental data summarizing compressivestrengths of cementitious materials containing pozzolanic compositionsthat include various sources of fly ash along with pumice.

FIG. 8B is a continuation of the table in FIG. 8A, experimental datasummarizing compressive strengths of cementitious materials containingpozzolanic compositions that include various sources of fly ash alongwith pumice.

FIG. 9 is a table of experimental data summarizing compressive strengthsof cementitious materials containing pozzolanic compositions thatinclude various sources of fly ash along with vitrified calciumalumino-silicate material (ground waste glass or fiberglass).

FIG. 10 is a table of experimental data summarizing compressivestrengths of cementitious materials containing pozzolanic compositionsthat include various sources of fly ash along with ultrafine (3 micron)pumice (Source No. 2).

FIG. 11 is an ASTM C618 certification demonstrating the conversion ofnon-spec fly ash into a certified Class F fly ash, according to someembodiments.

FIG. 12 is an ASTM C618 certification demonstrating the conversion ofnon-spec fly ash into a certified Class F fly ash, according to someembodiments.

FIG. 13 is an ASTM C618 certification demonstrating the conversion ofClass C fly ash into a certified Class F fly ash, according to someembodiments.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE DISCLOSURE

Certain embodiments of the present disclosure will now be furtherdescribed in more detail, in a manner that enables the claimed inventionto be understood so that a person of ordinary skill in this art can makeuse of the present disclosure.

Unless otherwise indicated, all numbers expressing reaction conditions,concentrations, yields, and so forth used in the specification andclaims are to be understood as being modified in all instances by theterm “about.” Accordingly, unless indicated to the contrary, thenumerical parameters set forth in the following specification andattached claims are approximations that may vary depending at least uponthe specific analytical technique. Any numerical value inherentlycontains certain errors necessarily resulting from the standarddeviation found in its respective testing measurements.

As used in this specification and the appended claims, the singularforms “a,” “an,” and “the” include plural referents unless the contextclearly indicates otherwise. Unless defined otherwise, all technical andscientific terms used herein have the same meaning as is commonlyunderstood by one of ordinary skill in the art to which this disclosurebelongs. If a definition set forth in this section is contrary to orotherwise inconsistent with a definition set forth in patents, publishedpatent applications, and other publications that are incorporated byreference, the definition set forth in this specification prevails overthe definition that is incorporated herein by reference.

The term “comprising,” which is synonymous with “including,”“containing,” or “characterized by” is inclusive or open-ended and doesnot exclude additional, unrecited elements or method steps. “Comprising”is a term of art used in claim language which means that the named claimelements are essential, but other claim elements may be added and stillform a construct within the scope of the claim.

As used herein, the phrase “consisting of” excludes any element, step,or ingredient not specified in the claim. When the phrase “consists of”(or variations thereof) appears in a clause of the body of a claim,rather than immediately following the preamble, it limits only theelement set forth in that clause; other elements are not excluded fromthe claim as a whole. As used herein, the phrase “consisting essentiallyof” limits the scope of a claim to the specified elements or methodsteps, plus those that do not materially affect the basis and novelcharacteristic(s) of the claimed subject matter. With respect to theterms “comprising,” “consisting of,” and “consisting essentially of,”where one of these three terms is used herein, the presently disclosedand claimed subject matter may include the use of either of the othertwo terms. Thus in some embodiments not otherwise explicitly recited,any instance of “comprising” may be replaced by “consisting of” or,alternatively, by “consisting essentially of.”

It has now been unexpectedly discovered that the addition of naturalpozzolans, as well as other previously identified pozzolans, enhancesthe chemical and pozzolanic performance properties of various fly ashes.Even more surprising, non-certifiable waste fly ash was so improved bythe addition of a natural pozzolanic agent, it was able to achieve aClass F (a better performing pozzolan than Class C) certification underASTM C618 and AASHTO 295. Furthermore, the added natural pozzolan didnot create any unexpected water demand in the fly ash. The added naturalpozzolan enhanced a poor-quality fly ash (Class F or Class C) ornon-spec fly ash to the point that it became a high-performance,certified Class F pozzolanic fly ash.

Whereas Class F pozzolanic fly ash is periodically in short supply incertain locations in North America, the discovery can extend diminishingClass F fly ash supplies. With over 150 coal-fired power plantsscheduled to be shut down or converted to natural gas in the nextdecade, Class F fly ash shortages will likely be exacerbated. Utilizingnatural pozzolanic agents (and other pozzolans) may allow for theextension or remediation/beneficiation of currently available fly ashsupplies, both certified and non-certified. Additionally, naturalpozzolanic agents may be used to convert Class C fly ash into a moredesirable Class F pozzolan.

The methods disclosed herein may facilitate the long-term availabilityof certified fly ash pozzolan, which is needed to produce economicallyviable, durable and chemically resistant concretes now, and in thefuture.

When a natural or other pozzolan is mixed with a poor-quality fly ash atan appropriate percentage (as disclosed in more detail below), apreviously non-certifiable fly ash is enhanced to a level that willallow for pozzolan certification via ASTM C618-12 and AASHTO M295.

When a natural or other pozzolan is mixed at an appropriate percentage(as disclosed in more detail below), Class C fly ash, a less-desirablepozzolan than Class F fly ash, may be converted to meet Class Fcertification requirements, a more desirable pozzolan.

A previously non-certifiable fly ash, mixed at an appropriate level witha natural pozzolan (or other pozzolans, as disclosed in more detailbelow), exhibits pozzolanic qualities that meet or exceed theperformance of most any currently certified fly ash available in NorthAmerica, Class F or Class C.

The present disclosure may facilitate the remediation of poor-quality,non-certifiable, currently wasted fly ash into a very useful Class Fpozzolan which may be certified under both ASTM C618-12 and AASHTO M295.Class F pozzolans are used in a great variety of concrete mix designs inorder to improve the concrete's performance characteristics. The presentdisclosure may also be used to remediate non-certifiable fly ash,enhancing it to a certifiable quality Class C or Class F fly ash. Thepresent disclosure may also be used to extend the quantities andavailability of good quality certified, Class F fly ash.

The present disclosure facilitates the removal of poor-quality fly ashfrom the waste stream or existing fly ash landfill/waste deposit andconverts it into a very useful product for which there is strong demandin the production of concrete for homes, buildings, and infrastructure.The present disclosure may also find use in oil field cementing slurriesused to secure oil well casings as well as prevent loss of oil to theformation during extraction.

The present disclosure may be used by cement companies to produce a “1Pcement.” 1P cements have been altered by the addition of a pozzolanicmaterial to provide pozzolanic advantages to the concrete in which it ismixed. Pozzolanic qualities include, but are not limited to: mitigatingone form of chemical attack or another, such as ASR, alkali-sulfatereactions, and the damaging effects of chloride ingress, particularlythe oxidation and debonding of reinforcing steel; concrete densificationand impermeability enhancement, increased long-term compressivestrength, and mitigation of efflorescence.

The present disclosure may be utilized by coal-fired generation plantsor their partners to enhance and remediate non-certifiable fly ash in amanner that would make the fly ash salable as a high performance Class Ffly ash, or with less remediation/beneficiation, a Class C fly ash. Thisrelates to fly ash that otherwise would be placed (or already exists) inwaste ponds or landfills, creating a direct cost in terms of daily andlong-term containment activities and an indirect cost in terms ofpotential environmental hazards that would stem from pond or containmentleaks, or the leaching of contaminants into soils and groundwater.

In some variations, the present disclosure provides a pozzolaniccomposition for use in concrete, the composition comprising fly ashcombined with a natural or other pozzolan. By “combined” it is meantthat the fly ash and natural pozzolan are physically mixed together;chemical reactions will typically not occur without the addition ofwater, although chemical combinations (such as equilibrium exchangereactions) are by no means excluded.

In some embodiments, the natural pozzolan is present in a concentrationof about 1 wt % to about 99 wt %, such as about 10 wt % to about 90 wt%, about 30 wt % to about 70 wt %, about 40 wt % to about 60 wt %, orabout 60 wt % to about 70 wt % of the pozzolanic composition. In variousembodiments, the natural pozzolan is present in a concentration of about1, 2, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85,90, or 95 wt % of the pozzolanic composition.

In various embodiments, the fly ash is present in a concentration ofabout 1, 2, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75,80, 85, 90, or 95 wt % of the pozzolanic composition.

The pozzolanic composition may or may not include components in additionto the fly ash and natural pozzolan. For example, additives oradmixtures may also be introduced. These additives may be added toadjust the properties of the pozzolanic composition itself, or toprovide admixture properties for the ultimate cement or concrete. Thepozzolanic composition may comprise an additive to adjust viscosity ofthe composition. The pozzolanic composition may further comprise anadditive to adjust water demand of the composition in concrete. Also,impurities may be present.

In some embodiments of the pozzolanic composition, a weight ratio of thenatural pozzolan to the fly ash is from about 0.01 to about 100, such asabout 0.1 to about 10, or about 1 to about 2. In various embodiments,the weight ratio of the natural pozzolan to the fly ash is about 0.02,0.05, 0.1, 0.2, 0.3, 0.5, 0.8, 1, 2, 3, 5, 8, 10, 15, 25, 50, 75, or 90,for example.

In this disclosure, a “natural pozzolan”, “other pozzolan,” “natural orother pozzolan,” and the like, should not be construed as limiting andrefers to any efficacious pozzolan that can function as a fly ashremediation agent. A “fly ash remediation or beneficiation agent” is anysupplementary cementitious material which possesses the chemical andphysical properties necessary to enhance, convert, or remediate a wastefly ash or a Class C fly ash. In preferred embodiments, the fly ashremediation or beneficiation agent converts a waste fly ash or a Class Cfly ash into a certifiable Class F fly ash, as defined by ASTM C618and/or AASHTO M295. Additionally, the fly ash remediation agent ispreferably able to remediate or enhance an already certified Class F flyash, such that when used as a pozzolan in concrete, the enhanced orremediated Class F fly ash will, generally speaking, extend supply,reduce set times, enhance early compressive strength, and strengthenmitigation properties against chemical attack, such as sulfate,chloride, and alkali-silica reactions.

The natural pozzolan may be a pozzolanic ash, such as (but not limitedto) a pozzolan derived from pumice or perlite. In some embodiments, thenatural pozzolan is selected from the group consisting of calcinedshale, calcined clay, metakaolin, and combinations thereof. The pozzolanmay be (or may be derived from) a high-quality Class F fly ash, groundglass, silica fume, or other materials.

In various embodiments, the natural or other pozzolan and/or othersupplementary cementitious materials may be selected from pumice(various size ranges), perlite, metakaolin, diatomaceous earth, silicafume, ignimbrites, ground granulated blast-furnace slag, vitrifiedcalcium alumino-silicates, ground waste glass, or combinations orderivatives thereof.

Pumice, called pumicite in its powdered or dust form, is a volcanic rockthat consists of highly vesicular rough textured volcanic glass, whichmay or may not contain crystals. Pumice is created when super-heated,highly pressurized rock is violently ejected from a volcano. Pumice iscomposed of highly micro-vesicular pyroclastic glass with thin,translucent bubble walls of extrusive igneous rock. It is commonly, butnot exclusively, derived of silicic or felsic to intermediatecomposition magma (e.g., rhyolitic, dacitic, andesite, pantellerite,phonolite, trachyte). Pumice is commonly pale in color, ranging fromwhite, cream, blue or grey, to green-brown or black.

Perlite is an amorphous volcanic glass that has a relatively high watercontent, typically believed to be formed by the hydration of obsidian.It occurs naturally and has the unusual property of greatly expandingwhen heated sufficiently. Scoria is another vesicular volcanic rock thatdiffers from pumice in having larger vesicles and thicker vesicle wallsand being dark colored and denser.

Silica fume is an amorphous, ultrafine powder that may be obtained fromsilicon-ferrosilicon alloy production. Ignimbrite is any of variousforms of ground stone, typically referring to a finely ground, nearlypure form of silica or silicate. Ground-granulated blast-furnace slag isobtained by quenching molten iron slag (a by-product of iron andsteel-making) from a blast furnace in water or steam, to produce aglassy, granular product that is then dried and ground into a finepowder. In some embodiments, vitrified calcium aluminio-silicatepozzolans may be made from recycled glass or fiberglass powders, fromfinely ground fresh glass powders, or a combination thereof.

In some embodiments, the natural or other pozzolan contains amorphoussilica, amorphous alumina, and iron. The natural or other pozzolan ofsome embodiments is selected for its silica content. The natural orother pozzolan of some embodiments is selected for its alumina content.The natural or other pozzolan of some embodiments is selected for itscombined silica/alumina and iron content.

In some embodiments, the natural or other pozzolan is selected for itshigh silica content and pozzolanic strength to be used as an additive toremediate poor quality fly ash to a degree that will transform thepreviously unusable fly ash into a useful Class F fly ash for use in theconcrete or cement industries.

In some embodiments, the natural or other pozzolan is selected for itsparticle-size distribution, surface area, particle-shape distribution,density, viscosity, or other properties. For example, pumice-derivedpozzolans may have an angular shape that creates higher water demandthan fly ash pozzolans, which tend to have a spherical shape thatcreates less water demand.

Natural or other pozzolans may also be inter-ground with fly ash (asopposed to simply blending), in order to achieve a remediated orenhanced fly ash. Inter-grinding would reduce the particle size of thefly ash while increasing the surface area. This method of fly ashremediation or enhancement would increase the pozzolanic reactivity ofthe fly ash, thus increasing the reactivity of the remediated orenhanced fly ash which includes the natural pozzolan.

In some embodiments, the pozzolanic composition is certified under ASTMC618-12 (“Standard Specification for Coal Fly Ash and Raw or CalcinedNatural Pozzolan for Use in Concrete”) as a Class F pozzolan. In theseor other embodiments, the composition may be certified under AASHTO M295(“Standard Specification for Coal Fly Ash and Raw or Calcined NaturalPozzolan for Use in Concrete”) as a Class F pozzolan. Both ASTM C618-12and AASHTO M295 are hereby entirely incorporated by reference herein. Itis also noted that pozzolanic compositions according to this disclosuremay be alternatively, or additionally, certified under other standardsor regulations, either presently existing or developed in the future, inthe U.S. or other countries.

This disclosure also provides a supplementary cementitious mixture,comprising a pozzolanic composition for use in concrete, the compositioncomprising fly ash combined with a natural or other pozzolan. Thepozzolanic composition provided by this disclosure may be incorporatedinto a concrete mix design, a cementitious mixture or other admixtures.Alternatively, instructions may be provided to introduce (combine) thefly ash and natural pozzolan components into a cementitious mixture orother admixture at a later time, for example, after mixing of primarycementitious products, aggregates, and water has already commenced.

In some variations, a concrete product or structure is provided,comprising the cementitious mixture as disclosed, or a reaction productthereof. In some variations, a concrete product or structure isprovided, comprising a pozzolanic composition or a reaction productthereof, wherein the pozzolanic composition comprises fly ash combinedwith a natural pozzolan. The concrete products or structures are notparticularly limited.

This disclosure also provides a method of producing a pozzolaniccomposition for use in concrete, the method comprising:

providing a source of fly ash;

providing a natural or other pozzolan; and

combining the fly ash with the natural or other pozzolan, to produce apozzolanic composition.

This disclosure also provides a method of upgrading a fly ash as apozzolanic material, the method comprising:

providing a starting fly ash;

providing a natural or other pozzolan; and

combining the starting fly ash with the natural or other pozzolan, toproduce an upgraded fly ash with enhanced pozzolanic properties comparedto the starting fly ash.

This disclosure also provides a method of converting a Class C fly ashto a Class F fly ash, the method comprising:

providing a certified or non-certified Class C fly ash;

providing a natural or other pozzolan; and

combining the Class C fly ash with the natural or other pozzolan, toproduce a Class F fly ash.

In some method embodiments, the natural or other pozzolan is present ina concentration of about 1 wt % to about 99 wt % in the pozzolaniccomposition, upgraded fly ash, or Class F fly ash. In certainembodiments, the natural or other pozzolan is present in a concentrationof about 10 wt % to about 90 wt %, such as about 30 wt % to about 70 wt%, about 40 wt % to about 60 wt %, or about 60 wt % to about 70 wt % inthe pozzolanic composition, upgraded fly ash, or Class F fly ash.

In these methods, the natural or other pozzolan may be selected from thegroup consisting of calcined or uncalcined pozzolanic ash (such aspumice-derived pozzolan) and perlite, calcined shale, calcined clay, DE,metakaolin, silica fume, and combinations thereof.

In some methods, the pozzolanic composition, upgraded fly ash, or ClassF fly ash is certified under ASTM C618-12. In these or other methods,the pozzolanic composition, upgraded fly ash, or Class F fly ash iscertified under AASHTO M295.

EXAMPLES

In these Examples, a wide variety of pozzolanic compositions comprisingfly ash combined with a natural or other pozzolan are evaluatedexperimentally for use in cementitious materials. Many sources of flyash and many pozzolan agents have been tested.

Type I/II cement (“TI-II” in the tables of FIGS. 1-10 ) is used for thecontrol (100%) and as 60%, by weight, of all other mixes used in thetesting program. The other 40 wt % of each mix is comprised of thevarious fly ashes, alone or in a remediated/enhanced configuration,using commercially available pozzolans as remediation agents.

Five separate fly ashes were remediated, converted, or enhanced in thetesting program described in these Examples:

Fly Ash Source 1=Class F Fly Ash, western U.S.

Fly Ash Source 2=Non-Spec Fly Ash, OK

Fly Ash Source 3=Non-Spec Fly Ash, CO

Fly Ash Source 4=Class C Fly Ash, TX

Fly Ash Source 5=Class C Fly Ash, MO

Class F Fly Ash was tested. One currently ASTM C618 certified F ash(Source 1) was remediated or enhanced using the invention. The certifiedfly ash was also used as a control compare to other remediated,converted, and enhanced certifiable F ashes against a currentlycertified F ash.

Non-Spec Ashes (waste) are defined as non-certifiable fly ash under ASTMC618 and AASHTO M295. Two non-certifiable ashes were used in thetesting, Fly Ash Source 2 and Fly Ash Source 3. These fly ashes wereremediated or beneficiated using a fly ash remediation agent in order toachieve C618 certification as a Class F fly ash (see FIGS. 11 and 12 ).

Class C Fly Ash was also tested. Two currently ASTM C618 certified ClassC ashes (Fly Ash Source 4 and Fly Ash Source 5) were remediated orconverted to certifiable Class F ashes using invention. These fly asheswere remediated or converted using a fly ash remediation agent in orderto achieve C618 certification as a Class F fly ash (see FIG. 13 forSource 4 results).

The following fly ash remediation agents have been evaluatedexperimentally in these Examples:

Pumice (90% passing 325 mesh)

Pumice (100% passing 325 mesh)

Pumice (3 micron—two independent sources, Source Nos. 1 and 2)

Metakaolin

Diatomaceous Earth

Silica Fume

Ignimbrites

Ground granulated blast-furnace slag (slag)

Vitrified calcium alumino-silicate material, ground waste glass

All samples were prepared in a mix where cement accounted for 60% of thecementitious material. The test regimen utilized a standard cementslurry mix design (no aggregate) for enhanced product differentiation.Water was mixed with the cement plus pozzolanic composition at about 18°C. degrees. The mixture was cured either at ambient temperature, about21° C. (water bath), or at about 38° C. At ambient temperature,measurements were made after 1, 7, and 28 days of curing time.

The mix design itself is a cement slurry (grout) design which allowedfor the use of 2″×4″ cylinders to produce the samples. This simplifiedthe batching and curing process in terms of time and available space.Also, no aggregate is included the mix design. These samples rely on thehydraulic and pozzolanic reactions and subsequent relative strengthsbetween the various cementitious ingredients alone. Also, by using afairly high 60/40 (cement/pozzolan) ratio, the relative strengths orreactivity of the assorted pozzolans are much more discernible.

The results are depicted in the tables of FIGS. 1-10 . The strength datashown is compressive strength in pounds/sq. inch (lbs/in² or psi). Eachtable shows the compressive strength of 100% TI-II cement mix (row 1)for reference purposes only, as well as the compressive strength of C618certified F ash (Fly Ash Source 1), as a control (row 2). Thecompressive strength at “1 Day” refers to a break test after curing thespecimen for 1 day at about 21° C. immersed in a temperature-controlledwater bath, “7 Days” refers to a break test after 7 days of curing thespecimen for 7 days at about 21° C. immersed, “28 Days” refers to abreak test after 28 days of curing the specimen for 28 days at about 21°C. immersed. The first data column shows the compressive strength undera break test after curing the specimen for 1 day at about 38° C.immersed.

All of the commercial pozzolans tested as fly ash remediation agentsprovided some degree of enhancement to the various fly ashes that weretested for compressive strength in over 100 batches of grout concrete.Class F fly ashes or natural pozzolans are added to cements andconcretes in order to enhance the concrete's chemical resistance againstsulfates, chlorides, and alkali-silica expansive reactions, and tomitigate against efflorescence. In most cases, pozzolans, includingClass F fly ashes, do not enhance compressive strength until after theusual 7-day and 28-day compressive strength tests have been completed.In other words, strength enhancement in a concrete using Class F flyash, versus a cement-only control, generally comes after at least 28 dayof curing. There are, however, exceptions in the testing wherein aremediated/beneficiated or converted fly ash actually surpassed controlin less than 28 days.

In all cases, it was discovered that by combining a natural or otherpozzolan with fly ash, thereby creating a remediated fly ash, thepozzolanic qualities of the fly ash were improved. This performanceenhancement was realized in terms of the ultimate compressive strengthof the concrete to which the remediated fly ash was added; and theincreased mitigation properties of the remediated fly ash in terms ofprotecting the host concrete from various forms of chemical attack(e.g., alkali-silica reaction, sulfate-induced expansion, and/orchloride ingress).

In all tested cases, dependent upon the exact mix ratio of natural orother pozzolan to fly ash, a non-spec fly ash was remediated to thepoint that it was able to be certified as a Class F pozzolan under ASTMC618 and AASHTO M295 specification standards. Without limitation, it isexpected that essentially any currently non-certifiable fly ashes can beremediated with the properly chosen natural pozzolan in order to meetASTM C618 certification for fly ash.

In all cases, dependent upon the exact mix ratio of natural pozzolan tofly ash, a certified Class C fly ash was successfully converted to allowfor the Class C ash to be reclassified to a more desirable pozzolanicclass of fly ash, namely as Class F fly ash (see FIG. 13 ). Withoutlimitation, it is expected, based on the data in these Examples, thatany certified Class C fly ashes can be successfully remediated andenhanced in order to meet ASTM C618 Class F certification standards.

Without limitation, it is also expected, based on this data, that anycurrently certified Class F fly ash can be enhanced in terms of theanticipated performance benefits when adding a pozzolan to a Portlandcement-based concrete, mortar, or grout.

It was also discovered that industrial byproducts, such as silica fumeand ground waste glass, can similarly enhance the performance of fly ashin terms of its use to improve concrete/mortar/grout compressivestrength and mitigation of chemical attack. It was also discovered thatground granulated blast furnace slag (referred to as “slag”) is able toenhance the performance characteristics of all forms of fly ash, bothcertified and uncertified.

Virtually every pozzolan enhances the various fly ashes to one degree oranother, some very significantly. Therefore, the conclusion from thedata in these Examples is that fly ash can be remediated by anypozzolan. A non-spec, normally wasted or land-filled fly ash can beremediated to an ASTM-certified pozzolanic Class F ash. AnASTM-certified Class C ash can be enhanced or converted to anASTM-certified Class F ash as well. In addition, the data show that arelatively poor performing spec F ash (Fly Ash Source 1) can be greatlyenhanced by the remediation or beneficiation process.

FIGS. 11 to 13 demonstrate proof that the remediation or beneficiationprocess works in terms of remediating or converting a non-spec ash or aspec C ash into a spec F ash. These figures include actual ASTM C618certifications, as certified by an industry-approved independentlaboratory. FIG. 11 shows non-spec ash, Fly Ash Source 3,remediated/beneficiated to a certified spec Class F fly ash. FIG. 12shows a non-spec ash, Fly Ash Source 2, remediated/beneficiated to acertified spec Class F fly ash. FIG. 13 shows a spec Class C fly ash,Fly Ash Source 4, beneficiated/converted to a certified Class F fly ash.

All publications, patents, and patent applications cited in thisspecification are incorporated herein by reference in their entirety asif each publication, patent, or patent application was specifically andindividually put forth herein.

In this detailed description, reference has been made to multipleembodiments of the disclosure and non-limiting examples relating to howthe disclosure can be understood and practiced. Other embodiments thatdo not provide all of the features and advantages set forth herein maybe utilized, without departing from the spirit and scope of the presentdisclosure. This disclosure incorporates routine experimentation andoptimization of the methods and systems described herein. Suchmodifications and variations are considered to be within the scope ofthe invention defined by the claims.

Where methods and steps described above indicate certain eventsoccurring in certain order, those of ordinary skill in the art willrecognize that the ordering of certain steps may be modified and thatsuch modifications are in accordance with the variations of thedisclosure. Additionally, certain of the steps may be performedconcurrently in a parallel process when possible, as well as performedsequentially.

Therefore, to the extent that there are variations of the disclosure,which are within the spirit of the disclosure or equivalents of theappended claims, it is the intent that this patent will cover thosevariations as well. The present disclosure shall only be limited by whatis claimed.

What is claimed is:
 1. A pozzolanic composition for use in concrete,said composition comprising coal ash combined with a natural pozzolan,wherein said natural pozzolan is present in a concentration of about 1wt % to about 99 wt %, and wherein said coal ash is a waste coal ashthat does not meet any specifications for pozzolanic mixtures, pozzolanadmixtures, or supplementary cementitious materials in concrete underASTM and/or AASHTO.
 2. The pozzolanic composition of claim 1, wherein aweight ratio of said natural pozzolan to said coal ash is from about0.01:1 to about 100:1.
 3. The pozzolanic composition of claim 1, whereinsaid natural pozzolan is a volcanic ash with pozzolanic properties. 4.The pozzolanic composition of claim 1, wherein said natural pozzolan isa material defined as a natural pozzolan pursuant to ASTM and/or AASHTO.5. The pozzolanic composition of claim 1, wherein the combination ofsaid natural pozzolan with said coal ash enhances the pozzolanic qualityof said coal ash.
 6. The pozzolanic composition of claim 1, whereinpozzolanic composition meets a specification under ASTM and/or AASHTOfor pozzolanic mixtures, pozzolan admixtures, or supplementarycementitious materials in concrete.
 7. The pozzolanic composition ofclaim 1, wherein said pozzolanic composition does not meet aspecification under ASTM and/or AASHTO for pozzolanic mixtures, pozzolanadmixtures, or supplementary cementitious materials in concrete.
 8. Apozzolanic composition for use in concrete, said composition comprisingcoal ash combined with a natural pozzolan, wherein said natural pozzolanis present in a concentration of about 1 wt % to about 99 wt %, whereinsaid coal ash is Class F coal ash under ASTM and/or AASHTO, and whereinsaid pozzolanic composition is a Class F pozzolan under ASTM and/orAASHTO.
 9. The pozzolanic composition of claim 8, wherein thecombination of said natural pozzolan with said coal ash enhances thepozzolanic quality of said coal ash.
 10. The pozzolanic composition ofclaim 8, wherein the combination of said natural pozzolan with said coalash maintains the pozzolanic quality of said coal ash.
 11. A method ofproducing a pozzolanic composition for use in concrete, said methodcomprising: providing a coal ash that is from a coal-fired power plant,a landfill, a waste or containment pond, or a combination thereof;providing a natural pozzolan; and combining said coal ash with saidnatural pozzolan, to produce a pozzolanic composition, wherein saidnatural pozzolan is present in a concentration of about 1 wt % to about99 wt %, wherein said pozzolanic composition meets a specification forpozzolanic mixtures, pozzolan admixtures, or supplementary cementitiousmaterials in concrete under ASTM and/or AASHTO.
 12. The method of claim11, wherein said combining said coal ash with said natural pozzolancomprises intergrinding said coal ash with said natural pozzolan. 13.The method of claim 11, said method further comprising subjecting saidcoal ash to a containment activity prior to said combining said coal ashwith said natural pozzolan.
 14. The method of claim 11, wherein saidnatural pozzolan is present in a concentration of about 10 wt % to about90 wt % in said pozzolanic composition.
 15. The method of claim 11,wherein said natural pozzolan is a material defined as a naturalpozzolan pursuant to ASTM and/or AASHTO.
 16. The method of claim 11,wherein said coal ash is a waste coal ash that does not meet anyspecifications for pozzolanic mixtures, pozzolan admixtures, orsupplementary cementitious materials in concrete under ASTM and/orAASHTO.
 17. The method of claim 11, wherein said coal ash is Class Ccoal ash under ASTM and/or AASHTO.
 18. The method of claim 11, whereinsaid coal ash is Class F coal ash under ASTM and/or AASHTO.
 19. Themethod of claim 11, wherein said coal ash is upgraded by the presence ofsaid natural pozzolan to enhance its pozzolanic quality prior toaddition of said pozzolanic composition to concrete.
 20. The method ofclaim 11, said method further comprising introducing said pozzolaniccomposition into a cementitious mixture.
 21. The method of claim 20,said method further comprising producing a concrete product comprisingaggregate and said cementitious mixture, or a reacted form of saidcementitious mixture.